Annual total emissions. The bars in this figure represent
carbon dioxide emissions for each year in PgC yr-1 from the specified region. The final bar, labeled 'Mean', represents the 2001-2010 average.
CarbonTracker models four types of surface-to-amosphere exchange of
CO2, each of which is shown in a different
color: fossil fuel emissions (tan),
terrestrial biosphere flux excluding fires (green), direct emissions from fires (red), and air-sea gas exchange (blue).
Negative emissions indicate that the flux removes CO2 from the atmosphere, and such sinks have bars
that extend below zero. The net surface exchange, computed as the sum
of these four components, is shown as a thick black line.

While CarbonTracker applies bottom-up estimates of fossil fuel and
wildfire emissions directly, it attempts to estimate optimal fluxes
from the ocean and land biosphere. This optimization starts with a
first guess of the flux component and its uncertainty (left panel).
The one standard-deviation level of uncertainty for the land flux is
shown with a thin green vertical line, and the uncertainty for oceanic
exchange is shown with a thin blue vertical line. The total
uncertainty, extending to the end of the vertical bar, incorporates
within-model and across-model uncertainties. This is due to the use
of the 8 prior flux models used in CT2011; within-model error is the
average posterior uncertainty from these eight simulations, and
across-model error is the additional uncertainty from the scatter of
the eight inversions. As shown in the legend, the within-model error,
which usually dominates the total error, is indicated by the small
horizontal cross bar in each vertical error bar. Fossil fuel
uncertainty is shown by the darker tan bar inset into the main fossil
bar. The two fossil fuel emissions estimates used in CT2011 are at
the ends of the darker inset bar.

The first-guess
fluxes are subsequently evaluated against atmospheric CO2 observations and modified to be consistent with
those measurements. The optimized results (right panel) have
different mean fluxes and reduced uncertainty ranges, indicating the
influence of information brought by the observations. The uncertainty
on the net flux (black vertical line) is the RMS sum of land biosphere
and oceanic flux uncertainties.

Results Summary (all units PgC yr-1)

Year

First Guess

Final Estimate

Fire Emission

Fossil Emission

Total Flux

2000

-2.40 ± 4.22

-2.99 ± 4.32

1.44

1.07 ± 0.02

-0.49 ± 4.32

2001

-2.03 ± 4.09

-2.01 ± 3.77

1.39

1.11 ± 0.02

0.50 ± 3.77

2002

-2.14 ± 4.01

-1.17 ± 3.34

1.73

1.14 ± 0.02

1.70 ± 3.34

2003

-2.41 ± 4.03

-1.57 ± 3.60

1.65

1.21 ± 0.02

1.29 ± 3.60

2004

-2.55 ± 4.04

-2.57 ± 3.80

1.77

1.29 ± 0.03

0.49 ± 3.80

2005

-2.05 ± 3.95

-1.29 ± 3.55

1.93

1.36 ± 0.03

2.00 ± 3.55

2006

-2.47 ± 4.04

-2.93 ± 3.77

1.84

1.40 ± 0.03

0.32 ± 3.77

2007

-2.33 ± 3.98

-2.11 ± 3.49

1.88

1.46 ± 0.03

1.24 ± 3.49

2008

-2.81 ± 4.06

-2.96 ± 3.87

1.40

1.52 ± 0.02

-0.03 ± 3.87

2009

-2.73 ± 4.00

-2.86 ± 3.88

1.36

1.55 ± 0.02

0.05 ± 3.88

2010

-2.73 ± 4.08

-2.42 ± 3.95

1.94

1.63 ± 0.02

1.15 ± 3.95

Mean

-2.43 ± 4.03

-2.19 ± 3.70

1.69

1.37 ± 0.02

0.87 ± 3.70

Results Summary. Annual and long-term mean (2001-2010) fluxes for the
specified region, by component. "First-guess" and "Final" are the
land biosphere (excluding fires) and ocean exchange fluxes before and
after optimization, respectively. The uncertainties listed for these
fluxes are one standard deviation confidence intervals. Fire and
fossil fuel emissions do not list uncertainties since they are imposed
without optimization in CarbonTracker. The "Total Flux" is the sum of
the final estimate, fire emission, and fossil emission columns.

Note that fossil fuel emissions can occur over regions characterized
as ocean or non-optimized regions such as ice, polar deserts, and
inland seas. This is partly due to real emissions from international
shipping, and partly due to emissions occurring in coastal land
regions that are assigned to the ocean in our coarse 1° x 1°
division scheme. Similarly, land regions may have a small
contribution from air-sea gas exchange, and vice versa.

Natural flux (top panel). First guess (red) and final (black) natural fluxes from the specified region, resolved by week. "Natural flux" is the sum of land biosphere, fire, and air-sea CO2 emissions to the atmosphere. It does not include fossil fuel emissions. Units are PgC yr-1. Faint background lines are the raw, weekly fluxes integrated over the specified region. The dark black and red lines in the foreground have been smoothed using a low pass filter. The filter used is an eight-week Hanning window, which has a similar frequency response to a four-week boxcar filter, but superior performance in attenuating high frequencies.

Fossil fuel flux (bottom panel). As in the top panel, but for fossil fuel emissions. Note that fossil fuel emissions are not optimized in CarbonTracker.